Method of and apparatus for synchronizing



Sept. 5, 1939. J NICHOLS 2,172,290

METHOD OF AND APPARATUS FOR SYNCHRONIZING Filed Jan. 2, 1929 4 Sheets-Sheet 1 6% Q l 5 fit, 6

ll. /z 9 INVENTOR.

. Harv a J/Vic77olu' ATTO Y p 5, 1939. H. J. NICHOLS 2,172,290

METHOD OF AND APPARATUS FOR SYNCHRONIZING Filed Jan. 2, 1929 4 Sheets Sheet 2 Acce/eraf/ny Arc l8 0 O o o o v (I, O l O INVENTOR. J Mekola' Sept. 5, 1939. H. J. NICHOLS 2,172,290

METHOD OF AND APPARATUS FOR SYNCHRONIZING Filed Jan. 2, 1929 4 Sheets-Sheet s l l f 'fl l l l'l l l INVENTOR.

p -5,1939. H. J. NICHOLS 2,172,290

METHOD OF AND APPARATUS FOR SYNCHRONIZING Filed Jan. 2, 1929 4 Sheets-Sheet 4 flaw" ATTO Patentedsept. 5, 1 939 UNITED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR SYNCHRONIZING Harry J. Nichols, Washington, I). 0., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application January 2, 1929, Serial No. 329,757

37 Claims.

This invention relates to the method of and apparatus for synchronizing and maintaining in synchronism two or more physically disconnected mechanisms remotely situated from each other. 1

The invention has particular adaptationto the synchronizing of two rotatable members employed at the sending and receiving stations, respectively, in the transmission of pictures or images by wire, called telephotography, or by radio, called television or radiovision, and in the following description will be described with relation to this latter application, although it is to be understood that without material modificatlon the apparatus and method are applicable to' other purposes.

In order that a clearer perception of the present invention and the objects sought to be accomplished thereby may be had, it is tobe stated that in the transmission of pictures or images by wire or by radio, in all methods now known, it is necessary to accomplish and maintain the synchronization of two periodically moving elements,.one at the sending station and one at the receiving station. In the most commonly used apparatus, the periodically moving elements at the sending and receiving stations are two motor-driven rotating discs called scanning discs, each carrying near its periphery a spiral row of equally spaced small holes. These discs, as is well understood by those familiar with the art, perform the function of breaking up into successive elements the picture or image being transmitted, such process being known as scan- 5 ning. Every known method utilizes comparable elements (equivalents to the above stated discs) and one of the essential factors in the successful transmission of pictures or images is to accurately synchronize such elements.

' The problem presented is in many respects distinct from that relating to the usual synchronization of alternating current machinery.

For example, in television apparatus complete synchronization requires the rotating elements to move at the same angular velocity and with an exact space phase relation without slipping or gaining, whereas ordinary synchronization merely requires that the machines have the same electrical frequency and an. approximate elec- 4 trical phase relation. Further, in television, transmission is limited to one direction and the amount of power which may be transmitted for synchronizing purposes is strictly limited by practical considerations.

Heretofore, in order to accomplish partial synchronization, a variety of methods and apparatus have been employed. In one method, it has been the practice to connect the motors driving the scanning discs, or equivalent elements, at both the sending and receiving stations to the same electrical power source, such as a public service power system or network. Hence, by using similar synchronous motors, the driving I motors may be maintained at the same speed by the common frequency of the power system, the necessary adjustments in phase being accomplishedmanually. In other methods, synchronization has been attempted by employing calibrated tuning forks, or crystal controlled electrical circuits, or other means for obtaining a constant or closely regulated frequency or speed, the necessary phase adjustments being accomplished manually. These latter methods have the inherent defect of long periods intervening between phase coincidences if the frequencies or speeds are almost, but not quite, equal, since the period between such coincidences equals the reciprocal of the difference between the two fre quencies or speeds. As a consequence, the speed and phase adjustments are very delicate. In 5 another method used, the motor driving the scanning disc at the sending station has been employed to drive a multipolar alternator generating an alternating current of relatively high frequency, which current was used to transmit. 3

} alternations over a separate wired or radio transmitting and receiving system, which alternations, after amplification, provided synchronizing current to a high frequency synchronous motor to produce speed synchronization of the scanning disc at the receiving station with that at the transmitting station. In this method, as well as most of the others, the synchronization as regards phase must be accomplished manually or by additional complicated apparatus. Because 0 of the difliculti'es and defects of the various partially automatic methods and the large amount of apparatus required, these have largely been displaced at present by manual speed and phase adjustments on the part of the operator at the receiving station. This is objectionable not only in that the attention of the operator must be given practically continuously to this duty but also in that a high degree of skill in manipulating the speed controls is required to accomplish anything like satisfactory results.

It is therefore an object of this invention to overcome the defects and disadvantages of present synchronizing methods of the class above referred toand to establish and maintain com 5 plete synchronization of two or more physically disconnected mechanisms or elements remote from each other, such as the scanning discs utilized in the transmission of pictures and images by radio. A further object is to accomplish such synchronization with the driving motors oi' the elements to be synchronized independent as to the source of power, and independent as to the character of the power supply, that is, either A. C. or D. C. supply may be used. A further object is to provide synchronizing apparatus of the above described character which is entirely automatic, and operative irrespective of whether or not the receiving motor is provided with a governor or other speed regulating device. A further object is to provide amethod of and apparatus for synchronizing which utilizes synchronizing impulses of low power within the transmission capacity of ordinary communication systems, the synchronizing impulse to be applied at frequent intervals, if so required. A further object is-to obviate the necessity of separate transmitting and receiving apparatus for transmitting the synchronizing impulses or alternations. A further object is to accomplish synchronization of radio vision or television apparatus by utilizing the picture transmitting apparatus with simple and inexpensive additions of equipment to produce the synchronization and in which synchronization is effected without interference with the picture transmitted.

A further object is to effect synchronization as above described with simple, inexpensive, and readily available apparatus of usual manufacture. A further object is to provide a method of synchronizing whereby one transmitting station may bring about automatic synchronization of an indefinite number of receiving stations. A further object is to effect immediate re-synchronization regardless of whether the transmitting or receiving stations depart from the desired speed. A further object is to graduate the speed regulating action applied to the elements or discs to be synchronized in proportion to the amount of corrective action required, that is, to apply successive accelerating or retarding impulses when the diii'erence in speed or phase is large and intermittent impulses when the differences are small. A further object is to provide synchronizing apparatus which avoids interference with the normal speed regulation except at such times as the speed of either the transmitting or receiving elements or discs depart from the desired speed. A further object is to accomplish the desired synchronization with a high degree of accuracy. A further object is to provide a method and combination of means which will cooperate in a practical and highly efficient manner to accomplisl accurate and complete synchronization of an tentire television transmitting and receiving sys- Other objects will be in part obvious from the annexed drawings and in part indicated from the following analysis of the invention, in which reference is made to the accompanying drawings illustrating an embodiment of my idea.

In the accompanying drawings Fig. 1 shows a schematic diagram of the A or sending station, omitting the details of the radio transmitting equipment, which may be of any suitable type or construction. v

Fig. 2 is a similar diagram of the B or ing station.

Fig. 31s a diagram of the scanning disc emreceivployed at the sending station, hereinafter referred to as disc A.

Fig. 4 is a diagram of the scanning disc employed at the receiving station, hereinafter referred to as disc B.

Fig. 5 is a diagram showing the application of the invention to the control of a non-synchronous motor, without speed governor.

Fig. 6 is a diagram showing the application of the invention to the control of a motor with speed governor.

Fig. 7 is a diagram of a modification oi the disc 28.

Fig. 8 is a diagram showing a simplified form of synchronizing control.

Referring to the drawings, and particularly to Figs.,l and 3, the elements of the A or sending station comprise a driver mechanism such'as a motor I which drives a scanning disc 2 which is generally of opaque material. The disc 2 contains the usual spiral row of image scanning holes I, and a synchronizing hole 4, positioned preferably on a diameter constituting the axis or medial line of a blank sector 5, situated between the two ends of the scanning spiral, although other locations may be found advantageous to suit the requirements of some equipments. (See Fig. 3.) Associated with the scanning disc is the image transmitting apparatus, consisting of a light source I and associated mirror 6a, a condenser lens I, a photo-electric cell 8, and amplifier 9, controlling the transmitter (not shown), the cooperation of these elements to control the transmitter being indicated in the diagram.

In addition to the image or picture transmitting apparatus, thereis associated with the scanning disc the synchronizing impulse transmitting apparatus, consisting of a source of radiant energy l0 (shown as a lamp) with a screen or shield I I having an aperture or slit i la disposed therein on the circumference traversed by the synchronizing aperture 4. An auxiliary photo-electric cell or other radiant energy reactive device I2 is arranged at the other side of the disc 2 so as to be affected by a beam through the aperture Ila and the synchronizing hole 4, and is connected to the amplifier 9 in parallel with the main photoelectric cell 8.

The operation of the picture transmitting ele-' ments is well understood and need not be here described. The operation of the apparatus for sending the synchronizing impulse is as follows.

For each revolution of the disc 2, the synchronizing aperture 4 passes between the light source l0 and the auxiliary photo-electric cell [2 during the brief interval between the successive scannings of the picture, at which instant an impulse I is transmitted from the sending station. Hence the synchronizing impulse may be transmitted over the same apparatus as the picture without interfering with the transmission of the picture.

While in the above description the synchronizing apparatus has been shown as separate from the picture apparatus, it is obvious that by means of prisms, mirrors, or lenses (not shown) the light from the main light source 6, as for example passing through a synchronizing opening disposed in the blank sector 5, may be directed to the photo-electric cell 8 to initiate the synchronizing impulse, and thus the synchronizing impulse may be transmitted without the auxiliary light source l0 and auxiliary photo-electric cell l2. All such variations or modifications are encompassed in the scope of the present invention.

For the purposes of the present invention, the

, with the picture transmission, a series of aper-' sage of energy from one to the other for the purpose of initiating a synchronizing signal or impulse, which impulse may be transmitted by wire, .or broadcast by a transmitting or sending station, at any desired wave length or frequency to an indefinite number of receiving stations.

Referring to Fig. 2, the B or receiving station consists of a receiver of suitable type (not shown) and amplifier l4 operating the television lamp I5, which may be of the neon, glow, or other quick response type, in such manner as to produce a response practically coincident with the reception of a signal or impulse from station A.

The receiving scanning disc It, to be known as the B disc, which is to be synchronized with the transmitting or A disc, is driven by a motor H or equivalent driving mechanism. By referring to Fig. 4, where this disc is shown in detail, it will be seen that it bears the usual spiral row of scanning holes 18 or equivalent, the ends of the scanning spiral being spaced to provide a blank sector I9 correspondingto blank sector of disc B, on the axis of which is another smaller blank sector 20, the arc of which is hereinafter referred to as the Synchronizing art: The scanning disc it is preferably of opaque material and has, at a suitable location so as not to interfere tures or windows 2| of various radiant energy transmitting capacities. These apertures are spaced by blank separators or pillars 22 which have a function in connection with speed regulation as well as their structural function. The apertures of larger capacity, such as those arranged on the accelerating arc are associated with speed acceleration and combine to form what is hereinafter termed the accelerating are. In a similar sense the apertures of lesser capacity are combined to form the retarding arc. Associated with these apertures is a 'prism or mirror 23, and a hole or slit 24a in a shield 24, for focusing on these apertures part of the energy emitted from the television lamp to a radiant energy reactive device, such as a photoelectric cell 25, adapted to control the speed of the driving motor IT to bring disc B into synchronism with disc A.

For the purpose of this invention, the essential elements associated with the utilization of the synchronizing impulses are means for receiving the synchronizing impulse, a radiant energy emitting device, an associated radiant energy reactive device, means such as the disc l6 and windows or apertures 2| for controlling, as by interrupting or completing the passage of energy from one to the other, and means associated with the energy reactive device to control the speed of the driver mechanism, thereby to establish and maintain disc B in'a synchronous relation with disc A.

The operation of the picture receiving apparatus is well understood and need not be here described. The operation of the apparatus for receiving the synchronizing impulse and applying it to bring disc B into synchronism with disc A is as follows:

Referring to Figs. 2 and 4, for each revolution of the disc A, a brief signal or impulse is sent out from the sending station A. These signals are received at station B and possibly other stations, and, after suitable amplification, appear as flashes of the television lamp [5 or similar device, the flashes of the lamp therefore having the same frequency as the disc A has revolutions, and occurring when the disc A has a def inite position of phase angle.

It is obvious that the signals may be sent out in any desired time or phase relation to the sending apparatus, so long as the proper periodic relations are maintained, and such variations or modifications are encompassed in the scope of the present invention.

Opposite to said television lamp IS, the photoelectric cell 25 is so arranged as to receive light passing from the lamp in definite amounts, or character, depending on the position of, the disc B. The televison lamp l5 will flash practically simultaneously with the passage of the synchronizing aperture 4 in the disc A across the slit I la. If the synchronizing arc of the disc Bis relatively opposite to the slit 24a at the instant when the lamp flashes, there is no effect on the photoelectric cell 25 which is masked by the 'blank sector of the disc B. Hence, as long as the discs are in synchronism, the motor rotates at the speed for which it is normally adjusted, without regulating effect due to the synchronizing impulse. Should the motor IT at B now'slightly increase its speed, the small hole 2| on the retarding arc will come into position opposite to the slit 24a at the instant the lamp flashes. Therefore, the photo-electric cell 25 will receive a certain amount of light from the lamp l5, which light, in a manner well understood, affects the flow of current in the plate circuit of the amplifier tube 26 (Fig. 5) thus partially energizing the relay 21, and thereby opening the break contact 28. This action breaks the circuit which short-circuits the resistance 30, thus increasing the resistance in series with the motor, and decreasing the motor speed. Thus the motor speed is slightly decreased and disc B again brought into synchronism with disc A. As soon as synchronism is again established, the blank sector 20 masks the photo-electric cell 25, interrupting further operation of the synchronizing control.

Conversely, should the motor I! slightly decreaseits speed, the large hole 3| (Fig. 4) on the accelerating arc will come into position opposite the slit 24a at the instant the lamp flashes; therefore, the photo-electric cell 25 will receive an increased amount of light, producing a larger flow of current in the plate circuit of the vacuum tube 26, thus completely energizing the relay 21, which opens the break contact 28 and closes the make contact 32, thus cuting out the resistances 30 and 33, in series with the motor. The motor will therefore receive more current, thus increasing its speed and returning to synchronism.

For the larger changes of speed the flash of the lamp l5 will occur when one of the slots of the retarding are or of the accelerating are are in position opposite the slit 25a, in which case the motor ll will receive a series of corrective impulses, quickly restoring synchronism.

A simple analysis willshow that similar corrective action will result when disc A increases or decreases its speed, hence B will follow A and maintain synchronism, regardless of whether the departure from the synchronous speed occurs at the sending or receiving station. A rheostat or I ment, either to accommodate large speed changes, as between stations of different periodicity, or to reduce the automatic corrective action.

For clearness in the above description it was assumed that the disc B was initially running in synchronism with disc A. However, assuming that the motor on being supplied with current is capable of running at synchronous speed, the motor will be regulated automatically to bring disc B into synchronism with disc A., During'the initial accelerating period, the motor receives additional accelerating impulses due to the action of the accelerating slots. The accelerating slots near the synchronizing arc become progressively shorter in length on account of the closer spacing of the pillars 22, hence as the synchronous relation is approached, the number of impulses is decreased, reducing the rate of acceleration,

ereby tending to bring the disc B smoothly to the synchronous speed without hunting. In a like manner, the slots on the retarding are are designed to graduate the retarding effect as synchronism is approached.

Referring to Fig. 5, wherein the motor is not fitted with a governor, the detailed operation of the automatic speed regulation for the motor is as follows.

The photoelectric cell is energized from the line and, as is well understood, the flow of current from the anode to the cathode is proportional to the amount of light received by the photoelectric cell. The change in current in the photoelectric cell circuit is amplified by the amplifier tube 26, in the plate circuit of which is placed the relay 21. As is well understood, the armature 21a of the relay 2! is maintained in the position shown by a light spring or other means (not shown), thus normally holding the break contact 28 closed and the make contact 32 open. On the passage of a certain minimum current, the armature 21a is attracted by the relay magnet, opening the contact 26, thus removing the short circuit from the resistance 36, thereby increasing the resistance in series with the motor and decreasing the motor speed. The amount of light from the lamp I5 is so controlled by the retarding slots and other well understood adjustments so made, that the action Just described results from the passage of the retarding slots between the slit 24a and photoelectric cell 25 at the instant the lamp I5 flashes, the relay again returning to the normal position on cessation of the flash from the lamp l5.

On receiving a larger amount of light, as through the accelerating slots, the relay 21 is completely energized, pulling the armature 21a home and closing the make contact 28, thereby short-circuiting the resistances and 33. This provides a path of low resistance for the motor current, which increases the motor current and also its speed.

For the purpose of explanation, the amount of light passing between the lamp l5 and the photoelectric cell 25, whereby the action of the relay 21 is controlled, has been described as being dependent upon the size of the holes or slots in the disc B. It is obvious, however, that the desired action of the relay 21 can be obtained by varying the amount or character of the light passing between the lamp l5 and the photoelectric cell 25 by interposing semi-transparent screens, color filters, or the like, over apertures of the same size, or by changing the position or direction of the transmitted beam, and all such adaptations for effecting the transmission of energy between the cooperating, radiant-actuated members to accomplish synchronization are encompassed in the scope of the appended claims. Likewise, the diagram shown as Fig. 5 is particularly adapted to motors with series-resistance speed control but it is obvious that the same principles can be applied to other types of motors adapted to speed control by varying the shunt-field current, or by a combination of these methods, and such adaptations are encompassed within the scope of the appended claims.

Referring to Fig. 6, the driving motor I! is here shown fitted with a governor 34 of the centrifugal type. As is well known, a governor of this type operates to keep the motor speed constant regardless of limited fluctuations of line voltage or of load, hence in order to accurately adjust the speed of the motor it is necessary to alter the equilibrium point of the centrifugal system. In the apparatus indicated, this may be done by an axial shift of the adjustable contact point 35. A simple analysis will show that raising the contact point 35 will increase the motor speed, while lowering it will have the opposite effect. The automatic speed control of the motor for purposes of synchronization is as follows.

The cooperation of the photo-electric cell 25, the amplifier tube 26 and relay 21 is similar to that described with reference to Fig. 5 except that the connections are adapted for direct current supply, whereas in Fig. 5 they are adapted to alternating current supply. When the relay 2! is partially energized through the agency of the retarding holes 2|, the relay armature 21a is attracted, springs 36. This energizes the polarized magnet 38, which lowers the contact point 35, thereby temporarily decreasing the motor speed. Likewise, when the relay 2! is completely energized, the relay armature 21a is pulled home rapidly, making and breaking contact 36 and closing contact 31, thereby energizing magnet 36 in opposite sense, which raises the contact point 35 and increases the motor speed.

Without further detailed explanation it is apparent that the synchronizing method and apparatus herein described are readily adaptedto the synchronization of driving motors fitted with speed governors.

In cases where motors of superior speed regulating qualities are used and where conditions of voltage, frequency and load permit, speed regulating apparatus even simpler than that heretofore described may be employed with satisfactory results following the method of synchronization described herein. Referring to Fig. 7, the scanning disc I6a at the receiving station is provided with the usual scanning holes l8 and with a single synchronizing aperture such as the slot 40, preferably located with one edge on the axis of the blank sector l9. Referring now to Figs. 6 and'8, it will be seen that the same connections to the photo-electric cell 25, amplifier tube 26, and relay 21 .are employed. The relay 21 (Fig. 8) may, however, be of simple type, its function beclosing the make-before-break ing to break the contact 28 whenever energized as a result of the synchronous flashes from lamp l5. This action breaks the circuit normally short-circuiting the adjustable regulating resistance 4| in the supply line of the motor H.

The operation of the synchronizing control is as follows:

The receiver synchronizing apparatus is actuated by the received synchronizing impulses as before described. When this method of control is to be used, the speed of the motor I! is normally adjusted to cause disc B to run slightly faster than disc A, which adjustment may be accomplished manually by means of the rheostat or variable resistor 29. Assuming that this adjustment has been made, the motor I! on bein started will accelerate and tend to attain sufficient speed to cause disc B to run ahead of disc A. During the acceleration period, should the synchronizing slot 40 appear between the slit 2411 (Fig. 2) and the photo-electric cell 25 at the instant of the synchronous flash of lamp 1 5, the relay 21 will operate to place the resistance 4! in the supply line, thereby reducing the motor current. However, since the resistance 4| is relatively small, such occurrences will not prevent the disc B reaching synchronous speed. On approaching synchronous speed, however, when the slot 40 comes into step with the synchronous flashes of lamp I5, the resistance 4| will be thrown successively into the supply line, thus checking the speed of the motor and causing the slot 40 to lag. When the lagging phase shift of slot 40 extends beyond the right edge as viewed in the figure, the relay 2! will cease to be energized by the synchronous flashes of lamp I and the motor will again tend to speed up, causing slot 40 to uncover and thus initiate a retarding action. This disc B will come into synchronism with disc A with the leading edge of slot 40 maintaining a slight oscillating or hunting action in respect to the synchronizing hole 4 of disc A. Provision is made for adjusting the amplitude and frequency of the hunting by varying the included section of the regulating resistance 4| and by manual adjustment of the rheostat 29, these adjustments being governed in practice by the range of speed fluctuations of the driving motors. A simple analysis will show that the proper corrective action results from a departure in speed of the disc A as well as of the disc B. In addition to the advantage of simplification, the method just described has the advantage of permitting the maximum range between the picture and synchronizing impulses, obviating any tendency of the picture impulses to interfere with the synchronizing action.

It will be perceived that I have provided a synchronizing method of superior characteristics, particularly as regards its adaptability to various conditions and as to accomplishing the manifold objects required of apparatus of this nature.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can by applying current knowledge readily adapt it for various applications without omitting certain features that from the standpoint of the prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalency of the following claims.

I claim:

1. In apparatus for the electrical transmission of pictures or images, in combination, a sending station to transmit electrical impulses and means including a periodically moving scanning element provided with a series of scanning openings, the scanning element being provided with a synchronizing aperture definitely related to the scanning openings, means including a source of radiant energy and a radiant energy reactive device associated with said aperture to transmit a synchronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures, a source of radiant energy which is energized upon the reception of the transmitted impulses, means reactive to energy from said source, and means operative automatically and regardless of the relative phase position of the last-named element with reference to the firstnamed element to establish a time and phase synchronous relationship between said elements, and thereafter to maintain such relationship.

2. 'In apparatus for the electrical transmission of pictures or images, in combination, a sending station to transmit electrical impulses and means including a periodically moving scanning element, means operatively related to said scanning element and including a source of radiant energy and a radiant energy reactive device to transmit a sychronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures, means associated therewith and responsive to the reception of the synchronizing impulses automatically and regardless of the relative phase position of the last element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established to establish and maintain said scanning elements in time and phase synchronism.

3. In apparatus for the electrical transmission of pictures or images, in combination, a sending station, and means associated therewith including a periodically moving scanning element to transmit electrical impulses, the scanning element being provided with a synchronizing aperture, means associated with said element and aperture and including a source of radiant energy and a radiant energy reactive device to transmit a synchronizing impulse definitely related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures, means associated therewith and responsive to the reception of the synchronizing impulses automatically and regardless of the relative phase position of the last element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established.

4. In apparatus for the electrical transmission of pictures or images, in combination, a sending station and means including a periodically moving scanning element to transmit electrical impulses, means operatively related to said scanning element and including a source of radiant energy to transmit a synchronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures, means associated therewith and responsive to the reception of the synchronizing impulses automatically and regardless of the relative phase position of the last element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established.

5. In apparatus for the electrical transmission of pictures or images, in combination, a sending .Staijion and means including a periodically moving scanning element to transmit electrical impulses, radiation actuated means associated with the sending station to transmit a synchronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures and a source of radiant energy which is energized upon the reception of the transmitted impulses, means reactive to energy from said source, means operative automatically and regardlesss of the relative phase position of the last element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established.

6. In apparatus for the electrical transmission of pictures or images, in combination, a sending stationand means including a periodically moving scanning element to transmit electrical impulses, radiation actuated means associated with the sending station to transmit a synchronizing impulse'related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element provided with a plurality of synchronizing apertures and a source of radiant energywhich is energized upon the reception of the transmitted impulses, means including a radiant energy reactive device and operative automatically and regardless of the relative phase position of the last element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established.

'7. In apparatus for the electrical transmission of pictures or images, in combination, a sending station and means including a periodically moving scanning element to transmit electrical impulses, radiation actuated means associated with the sending station to transmit a synchronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element and a source of radiant energy which is energized upon the reception of the transmitted impulses, and said last named scanning element being provided with a plurality of apertures adapted to transmit radiant energy emitted by the source of radiant energy upon the reception of the synchronizing impulses, means inclusive of a radiant energy reactive device responsive to the energy transmitted thru saidapertures, said means being operative automatically and regardless of the relative phase position of the last scanning element with reference to the first element to establish a time and phase synchronous relationship between said elements, and means tending to maintain such relationship after it has been established.

'8. In apparatus for the electrical transmission of pictures or images, in combination, a sending station and means including a periodically moving scanning element to transmit electrical impulses, radiation actuated means associated with the sending station to transmit a synchronizing impulse related to each cycle of motion of the scanning element, a receiving station including a periodically moving scanning element and a source of radiant energy which is energized upon the reception of the transmitted impulses, said last named scanning element being provided with synchronizing apertures of different radiant energy transmitting capacities disposed to transmit .energy emitted by said source of radiant energy ond named scanning element in time and phase synchronism with the first named scanning.

element.

9. A scanning disc for use in the reception of pictures or images, provided with a plurality of scanning openings and with a plurality of synchronizing apertures of different light transmitting capacities.

10. A scanning disc for use in the reception of pictures or images provided with a series of scanning openings spirally disposed therein and with a plurality of synchronizing apertures of different light transmitting capacities.

11. In apparatus of the class described, in combination, a sending station including a periodically moving element, and radiant energy actuated means associated therewith for initiating an electrical synchronizing impulse during each cycle of movement of said element, a receiving station including a periodically moving element provided with synchronizing apertures of graduated effect, and means, including a source of radiant energy operatively related to said apertures and responsive to the effect of the synchronizing impulse and said synchronizing apertures, to establish said second element in time and phase synchronism with the first element.

12. A scanning disc for use in the reception of pictures or images provided with a series of scanning openings spirally disposed therein, and with a plurality of synchronizing apertures definitely graduated in size.

13. In synchronizing apparatus for television, in combination, radiant energy actuated means responsive to radiant energy synchronizing impulses, a driving motor, a speed governor for said motor having a variable equilibrium point, relay means operatively associated with said radiant energy actuated device, and electromagnet means,

operatively associated with said relay means and said governor and operative to vary the equilibrium point of said governor in response to the variation in current through the energy actuated device.

'Theherein described method of establishing synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, translating the received impulses into speed corrective impulses of a magnitude whichvaries with any non-synchronous relationship of said elements, and applying said corrective impulses to the controlled element continually until synchronism is established.

15. The herein described method of establishing synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, translating said received impulses into speed corrective impulses of a magnitude and direction determined by any out-ofing synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, causing said impulses in cooperation with the controlled element to initiate speed corrective impulses of a magnitude which varies with any non-synchronous relationship of said elements, and applying said corrective impulses to the controlled element continually until synchronism is established.

1'7. The herein described method of establishing synchronism controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, causing said impulses in cooperation with the controlled element to inltiate speed corrective impulses of a magnitude and direction determined by any out-of-phase relation of said elements, and applying said corrective impulses to the controlled element continually until synchronism is established.

18. The herein described method of establishing and maintaining synchronism between periodically moving controlling and controlled ele ments, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, translating the received impulses into speed corrective impulses of a magnitude which varies with any non-synchronous relationship of said elements, applying said corrective impulses to the controlled element continually until synchronism is established, and, upon subsequent departure of said elements from synchronism, reapplying to the controlled element such corrective impulses of proper magnitude and direction as to reestablish synchronism.

19. The herein described method of establishing and maintaining synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, translating said received impulses into speed corrective impulses of a magnitude and direction determined by any out -of-phase relation of said elements, applying said corrective impulses to the controlled element continually until synchronism is established, and, upon subsequent departure of said elements from synchronism, reapplying to the controlled element such corrective impulses whereby to re-establish synchronism.

20. The herein described method of establishing and maintaining synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, causing said impulses in cooperation with the controlled element to initiate speed corrective impulses of a magnitude which varies with any out-oi-phase relationship of said elements, applying said corrective impulses to the controlled between periodically moving element continually until synchronism is established, and, upon subsequent departure of said elements from synchronism, reapplying to the controlled element such corrective impulses of proper magnitude and direction as to re-establish synchronism,

21. The herein described method of establishing and maintaining synchronism between periodically moving controlling and controlled elements, which consists in generating radiant energy synchronizing impulses each related to a predetermined phase position of the controlling element assumed during each cycle of its movement, transmitting and receiving said impulses, causing said impulses in cooperation with the controlled element to initiate speed corrective impulses of a magnitude and direction determined by any out-of-phase relation of said elements, applying said corrective impulses to the controlled element continually until synchronism is established, and, upon subsequent departure of said elements from synchronism, reapplying to the controlled element such corrective impulses whereby to reestablish synchronism.

22. In a view-transmission system, a transmitting station including a scanning device, a receiving station including a scanning device, means activated by the transmitting scanning device for deriving synchronizing electric impulses intermediate successive groups of electric impulses representing a view to be transmitted, a light source at the receiving station so disposed as to be controlled by said impulses, a photoelec-= trio-cell, means whereby a partially obstructed path is periodically established between said light source and said photoelectric-cell when said scanning devices are in synchronism, and means responsive to said photoelectric-cell for controlling the movement of said receiving scanning device, whereby a tendency toward an increase in the light-conveying capability of said path is compensated by deceleration of said receiving scanning device, and a tendency toward a decrease in the light conveying capability of said path is compensated by acceleration of said receiving scanning device.

23. In apparatus of the character described, a transmitting station including a periodically moving element, a receiving station including a periodically moving element, means for initiating periodically synchronizing signals each related to a period of motion of the first moving element, a light source at the receiving station so disposed 'as to be controlled by said impulses, a photoelectric-cell, means whereby a partially obstructed path is periodically established between said light source and said photoelectric-cell when said elements are in synchronism, and means responsive to said photoelectric-cell for controlling the movement of the second moving element, whereby a tendency toward an increase in the lightconveying capability of said path is compensated by deceleration of the second moving element and a tendency toward decrease in the lightconveying capability of said path is compensated by acceleration of said second moving element.

24. In a synchronizing system, the combination of means for receiving periodic synchronizing signals, a radiant energy source adapted to be energized by said signals, a periodically moving element to be synchronized, radiant energy reactive means, the element having provisions for establishing, when the element is moving in predetermined manner, a partially obstructed path of radiant energy between the energy source and related to a predetermined phase position of said element, and a receiving station including a periodically moving mechanical element, driving means therefor, means responsive for its actuation to the reception of said synchronizing signals for evaluating the phase relationship of said elements in terms of control efi'ects, and means for applying said control efiects to the driving means thereby automatically and regardless of such phase relationship to establish and maintain a synchronous relationship. between said elements.

26. In apparatus of the class described, in combination, a, sending station including a periodically moving element and means associated therewith for initiating aperiodic character signals and periodic synchronizing signals, each synchronizing signal being related to a predetermined phase position of said' element, and a receiving station including a periodically moving element adapted to distribute the received signals, means responsive to the synchronizing signals determining and translating the phase relationship of said elements into controlling effects, and means operative solely in response to the controlling efiects for establishing and maintaining a time and phase synchronous relationship between said elements automatically and regardless of the relative phase position of said elements.

27. In apparatus of the class described, in combination, a sending station including signal distributing means adapted to initiate aperiodic character signals and periodic control signals, and a receiving station including signal distributing means, means including a radiant energy device responsive for its actuation to the reception and distribution of the control signals for determining the phase relationship of said signal distributing means, and means control-led solely by said last means for establishing a time and phase synchronous relationship between said distributing means automatically and regardless of the relative phase position of said distributing v means.

28. The herein described method of establishing a synchronous relationship between periodically moving, remotely situated controlling and controlled elements, which consists in the steps of initiating control signals each related to a fixed phase position of the controlling element as it moves through each of its successive cycles of movement, transmitting and receiving said signals to control the energization of a radiant energy emitting device, passing the so emitted energy to a radiant energy reactive device in an amount which is a function of the phase relationship of said elements for each cycle of their movement, and controlling the rate of movement of the controlled element in accordance with the reaction of the reactive device, thereby automatically to establish the desired synchronous relationship.

29. The herein described method of establishing a synchronous relationship between periodically moving, remotely situated controlling and controlled elements, which consists in the steps of initiating control signals each related to a fixed phase position of the controlling element 'as it moves through each of its successive cycles of movement, transmitting and receiving said signals, and utilizing said signals and any out-ofphase relationship of said elements as exists at the instant of reception of said signals to directly control the rate of movement of the controlled element, thereby automatically to establish the desired synchronous relationship.

30. The herein described method of establishing a synchronous relationship between periodically moving, remotely situated controlling and controlled elements,.which consists in the steps of initiating control signals each related to a fixed phase position of the controlling element as it moves through each of its successive cycles of movement, transmitting and receiving said signals, and utilizing said signals in accordance with such out-of-phase relationship of said elements as exists at the instant of reception of said signals to directly control the rate of movement of said controlled element, thereby automatically to establish the desired synchronous relationship. 7

31. The herein described method of establishing a synchronous relationship between periodically moving and remotely situated controlling and controlled elements which consists in the steps of initiating control signals of similar characteristics, each related to a period of movement of the controlling element, transmitting and receiving said impulses,'and utilizing. the received signals and any non-synchronous relationships between said element as may exist at the instant of signal reception to so control the rate of movement of the controlled element as automatically to establish the desired synchronous relationship.

32. The herein described method of establishing a synchronous relationship between remotely synchronizing signals having similar character I istics, transmitting and receiving said signals, and utilizing the received signals and any non= synchronous relationship between said elements which exists upon the reception of the signals and at any time during the operation of the controlled signal-distributing means to establish automatically the desired synchronous relationship.

33. In apparatus of the character described, in combination, a sending station including a periodically moving scanning element, a source of radiant energy, and a radiant energy reactive device operatively related thereto, the scanning element being operative periodically to pass an energy beam from said source to said device whereby to initiate synchronizing impulses of similar characteristics, each said impulse bein related to a cycle of motion of the scanning element, a receiving station including a periodically moving scanning element, driving means there for, means responsive to the received synchronizing impulses for evaluating the phase relationship of said scanning elements in terms of control effects, and means for applying said control efiects to the driving means thereby automatically and regardless of such phase relationship to establish and maintain a synchronous relationship between said scanning elements.

34. In apparatus of the character described, in

combination, a sending stationadapted to trans- 7 mit electrical character and synchronizing impulses and including a periodically'moving scanning and synchronizing element, a source a radiant energy and a radiant energy reactive device for initiating periodically synchronizing impulses of similar characteristics, each said impulse being related to a cycle of motion of the scanning element, a receiving station including a periodically moving scanning and synchronizing element, driving means therefor, means including a radiant energy device which is responsive to the received synchronizing impulses for evaluating the phase relationship of said scanning elements in terms of control effects, and means for applying said control effects to the driving means, thereby automatically and regardless of such phase relationship to establish and maintain a synchronous relationship between said scanning elements.

35. In apparatus of the character described,

in combination, a sending station including a periodically moving scanning element, a source of radiant energy and a radiant energy reactive device operatively related thereto, the scanning element being operative periodically to pass an. energy beam from said source to said device whereby to initiate synchronizing impulses of similar characteristics, each said impulse being related to a cycle of motion of the scanning element, a receiving station including a periodically moving scanning and synchronizing element, driving means therefor, means including a radiant energy device which is responsive to the received synchronizing impulses for evaluating the phase relationship of said scanning elements in terms of control effects, and means for apply ing said control effects to said driving means thereby automatically and regardless of such phase relationship to establish and maintain a synchronous relationship between said scanning elements.

36. In apparatus for the electrical transmission of characters, in combination, a sending station including cyclically moving scanning means and means associated therewith for initiating periodic electrical synchronizing signals of predetermined characteristics, each signal having a predetermined relationship with reference to the beginning of a cycle of movement of said scanning means, a receiving station including receiving scanning means, means responsive to the received synchronizing signals for evaluating the phase relationship of said scanning means, and means actuated solely by said last means for applying corrective control effects in accordance with such evaluation to the receiving scanning means, thereby automatically and regardless of the existing phase relationship to establish a desired synchronous relationship between said scanning means.

3'7. In a visual communication system, the herein described method of establishing a predetermined synchronous relation between cyclically moving and remotely situated controlling and controlled scanning means, which consists in the steps of generating periodic control signals of predetermined characteristics, each having predetermined relation with reference to the beginning of a cycle of movement of the controlling scanning means, transmitting and receiving said signals, utilizing said received signals to evaluate the phase relationship of said scanning means, and applying corrective control effects in accordance with such evaluation to the controlled scanning means thereby automatically and regardless 

